does not depend on the pressure applied to it (i.e. liquids are incompressible).
The volumetric flow rate of the gas, however, is significantly greater following the pressure-reducing
valve than before, since the reduction in pressure allows the gas to expand (i.e. less pressure means
the gas occupies a greater volume).
What this tells us is that volumetric flow measurement for gas is virtually meaningless without
accompanying data on pressure and temperature. A flow rate of “430 ft3/min” reported by
a flowmeter measuring gas at 250 PSIG means something completely different than the same
volumetric flow rate (430 ft3/min) reported at a different line pressure.